Motor vehicle suspension systems are configured to follow elevational changes in the road surface as the vehicle travels. When a bump or other rise in the road surface is encountered, the suspension system responds in “jounce,” quickly moving upward relative to the frame of the vehicle. Similarly, when a dip in the road surface is encountered, the suspension responds in “rebound” such that the wheel moves downward relative to the frame of the vehicle.
During either a jounce or rebound event, a spring (e.g., a coil, leaf, or torsion spring) incorporated at the wheel provides a response to the resulting vertical movement. In order to prevent wheel bouncing and excessive vehicle body motion, however, a damper (i.e., shock absorber, strut, etc.) at the wheel dampens this motion.
Vehicle suspension engineering has traditionally focused on ride and handling as it pertains to body and wheel relative motion below about 1.5 m/s (meters per second). However, the suspension travel requirements in a vehicle are primarily driven by severe events, which can cause significant displacement of the wheel relative to the body. Such events, as when the vehicle encounters a deep and steep-walled pothole, can generate wheel velocities (relative to the body) of up to 9.0 m/s.
Progressive damping provides one strategy for reducing harsh impacts during severe events, and generally involves maintaining a predefined load in jounce and reducing engagement into the jounce suspension stop or other such structure. However, known progressive damping systems have thus far been unsuccessful in fully addressing the challenges posed by real-world road conditions.
For example, most gas-charged hydraulic dampers produce regressive resistance at higher velocities due to the limited pressure supported by the gas spring. Increased gas charge pressure increases seal friction, reducing durability and increasing ride harshness. Furthermore, During severe road events, insufficient pressure under the column of hydraulic oil prevents its flow through the piston, as the floating piston tends to move further than necessary to accommodate the changing volume, making the damper less capable of absorbing the input energy.
Accordingly, it is desirable to provide suspension systems that produce acceptable ride quality during routine conditions while accommodating severe road events. It is also desirable to reduce total jounce travel so that a given vehicle can be trimmed lower, thereby enabling competitive styling cues. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.